Eritoran, which is also referred to as “E5564”, is a lipopolysaccharide analog comprising two sugar moieties and four long chain fatty acid moieties. Eritoran has a molecular weight of about 1,401. Methods for preparing eritoran are described in U.S. Pat. Nos. 5,530,113; 5,681,824; 5,750,664; 5,935,938; and 6,184,366, and in WO 96/39411. Those documents are incorporated by reference herein. Eritoran drug formulations with varying micelle hydrodynamic diameters have reportedly been achieved by controlling pH and concentration of counter-ions in a solution. That is reported in U.S. Pat. No. 6,906,042, which is incorporated by reference herein.
Eritoran is a Lipid A analog that acts as a Toll-like receptor 4 (TLR4) antagonist. Eritoran has the following structure:

The activity of Lipid A analogs has been reported to be altered by interactions with lipoprotein cholesterol. These lipoproteins are typically present in human serum and include low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). A study has postulated that changes in plasma lipoprotein profiles can alter both efficacy and pharmacodynamics profiles of lipophilic drugs. In particular, the study noted that binding of eritoran to HDL resulted in time-dependent loss of drug activity. See Daniel P. Rossignol, et al., “Safety, Pharmacokinetics, Pharmacodynamics, and Plasma Lipoprotein Distribution of Eritoran (E5564) during Continuous Intravenous Infusion into Healthy Volunteers” Antimicrobial Agents & Chemotherapy, September 2004, p. 3233-3240, which is incorporated by reference herein.